Hydrocarbon conversion processes often employ multiple reaction zones through which hydrocarbons pass in a series flow. Each reaction zone in the series often has a unique set of design requirements. A minimum design requirement of each reaction zone in the series is the hydraulic capacity to pass the desired throughput of hydrocarbons. An additional design requirement of each reaction zone is sufficient heating to perform a specified degree of hydrocarbon conversion.
One well-known hydrocarbon conversion process is catalytic reforming. Generally, catalytic reforming is a well-established hydrocarbon conversion process employed in the petroleum refining industry for improving the octane quality of hydrocarbon feedstocks. The primary products of reforming are a motor gasoline blending component or aromatics for petrochemicals. Reforming may be defined as the total effect produced by dehydrogenation of cyclohexanes and dehydroisomerization of alkylcyclopentanes to yield aromatics, dehydrogenation of paraffins to yield olefins, dehydrocyclization of paraffins and olefins to yield aromatics, isomerization of n-paraffins, isomerization of alkylcycloparaffins to yield cyclohexanes, isomerization of substituted aromatics, and hydrocracking of paraffins. A reforming feedstock can be a hydrocracker, straight run, FCC, or coker naphtha, and it can contain many other components such as a condensate or thermal cracked naphtha.
Heaters or furnaces are often used in hydrocarbon conversion processes, such as reforming, to heat the process fluid before it is reacted. The heaters can be located before the first reaction zone and/or between reaction zones. Generally, most of the fired heaters or furnaces have a U-tube configuration with end fired burners. The fired heater box typically contains 3 or 4 cells made up of the charge heater and 2 or 3 interheaters. The inlet and outlet manifolds for all of the fired heater cells are at the same height.
It can be difficult to arrange all of the manifolds at the same height because of layout issues associated with the intersection of two or more pipes connecting the reaction zones and heater cells. It may be necessary to include additional straight lengths of piping and piping fittings, such as 45 degree and 90 degree elbows, so that all of the manifolds are at the same height. The additional piping can significantly increase the capital cost of the reaction zone sections because of the size of the pipe and the materials it is made of.
Therefore, there is a need for reaction zones including fired heaters having reduced costs.